Recently, semiconductor manufacturing process has downed to the 16/14 nm scale, namely, advanced to the nodes below 10 nm, and adopting transistors with a three-dimensional structure, such as a fin-shaped field effect transistor (Fin-FET) with treating a group III-V and a germanium as its channel materials. Since the III-V group semiconductor wafer material can provide ten to thirty times higher electron mobility and the germanium provides more than four times higher hole mobility, than that of silicon material, whereby gate leakage current problem of the transistor can be effectively controlled, and the electron mobility can be raised, which can significantly enhance the chip operation performance, and at the same time reduce the power consumption. Therefore, various applications for the III-V group compounds, especially germanium (Ge), silicon-germanium (SiGe) and so forth are highly expected.
In sub-micron semiconductor manufacturing process, chemical mechanical polishing (CMP) is usually used to achieve global planarization on a wafer surface. However, in metal CMP technique, metal dishing, erosion, corrosion and other polishing flaws often occurred on a metal surface. To carry out the CMP to the above mentioned Fin-FET which adopted silicon-germanium as its primary material, for example, a Fin-FET structure published in US patent US 2011/0291188 A1 and US 2012/0168913 A1, silicon, silicon-germanium and silicon dioxide substrates thereof will be simultaneously grinded so that the removal ratio of the above-mentioned substrates will be restricted.
US Pat. US2012/0190210 A1 discloses that presently CMP slurry used for polishing silicon substrate usually contains ammonia-like pungent odor of ethylenediamine, other amines, or hydrofluoric acid which brings highly dangerous for human exposure. In view of this, it is necessary to develop a non-odor and hydrofluoric acid free polishing composition, which can effectively enhance the removal rate of silicon-containing substrate, and still does not cause severe corrosion to the grinding objects.
Please refer to Table 1, which is a chart of collecting contrast examples, with using a polishing composition consisting of hydrogen peroxide and ethylenediamine for polishing silicon-germanium substrate (the silicon-germanium substrate contents 10% to 80% of germanium), silicon substrate, and silicon dioxide substrate, wherein the hydrogen peroxide is used as an oxidant and the ethylenediamine functions as a catalyst. In general polishing applications, the oxidant is used to produce a easily removable oxide layer on the metal substrate, an inhibitor is configured to block the oxidation reaction, the catalyst is used to facilitate the removal of metal, and a surfactant is used to prevent abrasive particles from aggregating and to provide lubricating effect so as to reduce scratching defects, and a buffer is used to keep pH value stable at a nearly constant.
A Polishing test were conducted according to the following conditions. The result is recorded on Table 1.
Polishing machine: Mirra 8″ Polish
Polishing pad: IC1010
Clean solution: deionized water
Wafer: SiGe blanket wafer, tetraethylortho silicate (TEOS) blanket wafer, bare silicon blanket wafer
Polishing time 1 min.
Head DF: 1.5 psi
Platen/head speed: 73/67 rpm
TABLE 1SiO2 Hydrogen SiO2contentPeroxideEthylenediamineSi R.RSiGe R.R.R.R.SiGe SER(wt %)(wt %)(ppm)(Å/min)(Å/min)(Å/min)(Å/min)Contrast example 111028245012503Contrast example 21010004210280Contrast example 311100045250028497Contrast example 4115000145252020489
In Table 1, a static etching rate (SER) of the silicon-germanium substrate is obtained by calculating the weight difference in a manner of placing a 3 cm×3 cm silicon-germanium substrate into the polishing composition for 5 minutes. As shown in the contrast examples 1-4 of table 1, adopting hydrogen peroxide as the oxidant can obtain a silicon-germanium removal rate (RR) greater than 2000 Å/min but a static etching rate near to 500 Å/min that may cause surface corrosion to the above mentioned substrates. Furthermore, adding ethylenediamine as the catalyst to enhance the removal rate of the silicon substrate is also limited. Therefore, using the hydrogen peroxide as the oxidant cannot effectively control the removal rate and the static etching rate of various substrates.